1. Field of the Invention
The present invention relates to an injection molding apparatus. More specifically, it relates to an injection molding apparatus provided with a die having a hot nozzle that is in communication with a cavity, and a manifold formed by hot runner connected to this hot nozzle.
2. Related Art
Heretofore, an injection molding apparatus has been known that performs injection molding of thermoplastic resins. This injection molding apparatus is provided with a die having a hot nozzle that is in communication with a cavity, a manifold formed by hot runner connected to this hot nozzle, and a cylinder device that supplies molten resin to this hot runner.
A heater that heats the hot runner is built into the manifold.
A communication passage that communicates with a cavity surface is formed in the die.
The hot nozzle has a nozzle body of a cylindrical shape that is inserted into the communication passage of the die, and a flange portion formed at one end of this nozzle body that is exposed outside of the communication passage.
A band heater that heats the hot nozzle is provided between the communication passage and the nozzle body of the hot nozzle (refer to Patent Document 1).
According to the above injection molding apparatus, the hot runner is heated by the heater built into the manifold, and the hot nozzle is heated by the band heater. In this state, molten resin is supplied to the hot runner by the cylinder device. Then, this molten resin passes through the hot runner and hot nozzle, and is filled into the cavity of the die.
Incidentally, expanding color variation in molded articles has been demanded due to consumer tastes having diversified in recent years.
In order to solve this problem, although techniques have been considered in which a plurality of injection molding apparatuses is provided and that produces a molded article of differing colors for each injection molding apparatus, a plurality of dies become necessary, and thus the cost is high due to the equipment increasing in size.
Then, a technique has been proposed in which a plurality of cylinder devices that supply molten resin of different colors is prepared, and these cylinder devices are connected to one manifold (refer to Patent Document 2). According to this technique, molded articles of different colors can be produced in one die by selectively driving the cylinder devices.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. H11-28743    [Patent Document 2] Japanese Examined Patent Application No. S60-29616